The present invention relates to a system and method for separating recyclable material. Specifically, the present invention relates to a method and system for separating recyclable debris which includes ferrous material, fines, non-ferrous heavy material, and non-ferrous light material.
The first step in recycling is to separate the various types of materials into homogeneous fractions. The ferrous materials include tin cans and other metal materials. Glass may be present in small broken pieces, referred to as fines, or as intact bottles, referred to as non-ferrous heavy material. Aluminum cans and various forms of plastic, such as plastic containers and bottles, form the bulk of the non-ferrous light material.
The recycling industry uses a broad variety of separation techniques to separate recycled debris. Workers in the field have used both manual and automatic techniques. Manual techniques which involve human sorters are usually not cost effective. Automatic techniques which rely on sorting by fraction size, magnetic characteristics, or density for air separation have generally not been employed by industry in a manner which minimizes the need for human sorters. Those in the field have found that achieving high quality separation within reasonable cost limits proves to be an unmet need. Because municipal waste varies widely in geographical as well as daily make-up and consistency, a need remains for a uniform separation system.
One attempt at providing uniform separation of municipal waste into various fractions is described in U.S. Pat. No. 5,234,109 to Pederson. Pederson teaches a method where materials are first magnetically separated, thereafter separated by size using a vibrating screen and then air blown by a sorter so as to blow the lighter materials away from the heavier materials. The vibrating screen used by Pederson is susceptible to plugging and jamming which results in significant down time for maintenance and repairs. In addition, it requires considerable structural support, at considerable capital cost, to withstand the stresses caused by the continuous vibration. Moreover, air blowing as taught by Pederson, is an inefficient method for separating materials. It is difficult to control and produces copious amounts noise and dust, which fous machinery and causes safety and health problems for the human operators and sorters.
Thus, a need remains for a system which provides uniform separation of municipal wastes while avoiding the problems encountered by workers in the field. Accordingly, it is an object of this invention to provide such a system.